It is well know to employ automated optical inspect systems to inspect electrical circuits such as printed circuit boards (PCB) for defects at various stages of fabrication. An important stage in fabricating electrical circuits is the deposition of solder paste onto a PCB, prior to mounting of electronic devices such as microchips and other semiconductor devices. In fact, a substantial percentage of defects in electronic devices can be attributed to defects associated with problems related to the deposition of solder paste. Early identification of these problems can result in a considerable cost savings to a manufacturer of electronic devices.
Various factors are commonly recognized as determining the quality of solder paste deposits, including: position accuracy of each solder paste deposit over a solder pad; average thickness of a solder paste deposit; and differences in the volume of each solder paste deposit.
Consequently, an effective system for automatically optically inspecting solder paste deposits should to be able to precisely determine both 2 dimensional as well as topographical information (height information for various locations) relating to the surface of a printed circuit board onto which solder paste has been deposited. This information needs to be sensed and processed at a high speed in order to avoid forming a bottle neck during the assembly of electronic components onto an assembled electronic circuit device.